After solving some problems (explained here: link) I finally managed to run through the complete update procedure. After the installation my smartphone reboots and is completely reset - as espected.
Great! Now all I need to do is to copy back my backup and then take care of the one or the other setting that may not have been taken over correctly - I thought.
Well .. I was disappointed badly. I have no idea why but my phone is completely reset but is still running the old firmware version:
400.21.013 22-10-2009 RM-346 Nokia E71-1 (231.05)
And Nokia OVI Suite keeps insisting that there is a new firmware for my phone.
I don't have the slightest idea what's wrong. Maybe Nokia has uploaded a wrongly labeled old firmware to their server by accident.
What I do know - this problem will cost me time.